Thursday, February 28, 2008
Big Blue Saw is a service bureau that does waterjet cutting of metal and plastic. They cut very thick pieces of metal, which surprises me, I didn't know you could do that.
A couple more: Fabjectory.com specializes primarily in making physical copies of avatars from games like SecondLife. FluidForms makes pretty flowing shapes for things like vases and pitchers. I haven't read about these yet, and as of this writing I don't know what technology they use, or what design software.
How many of these gadgets could be self-replicative in the RepRap sense? For example, could one use a laser cutter (or a laser-cutting service like Ponoko) to cut out pieces and use those pieces to build another laser cutter, thereby driving down the cost of laser cutters? As with RepRap there will inevitably be complicated pieces that can't be made that way. CO2 lasers are dangerous and expensive, so I don't think this could make the kind of impact in the developing world that RepRap hopes to make. A replicating CNC machine might be a better bet, as Dremel tools are much cheaper and safer than lasers.
That self-replicative idea does fascinate me a good deal. It will, over time, drive down the price of the self-replicating thing. That doesn't mean we'll enter a microeconomic paradise, but it promises at least to be interesting and possibly to raise the quality of life noticeably.
I've haven't blogged too much about commercial machines. I want to do more of that. I admire the hobbyists and their perseverance in the face of difficulties, but the technology appearing in commercial machines will gradually trickle down into the hobbyist arena as patents expire.
Wednesday, February 27, 2008
Toby Borland (of SMARTlab in the U.K.) has designed a set of laser-cut plywood RepRap parts and made the EPS files available on the Ponoko website. There is a Flickr photo set showing laser-cut RepRap parts and the process of assembling them; I am not sure that's the same Ponoko files and process, or another laser-cutting effort, but it gives you a sense of what's involved, and the level of complexity.
Friday, February 22, 2008
Around 2000, Andrew Turberfield (Oxford University's Department of Physics) used DNA to make tweezers, with arms 7 nanometers long.
"Of course it's all very speculative," said Dr Turberfield, "but you can imagine, for instance, little factories on chips doing chemistry or simple assembly. You can think of production lines made up of little motors with different reactants being passed from one place to the next."Things got really interesting in March 2006 with Paul Rothemund's DNA origami technique. Here is the publication. I was working at Nanorex at that time, and we were all quite excited about it.
In 2005 Turberfield and colleagues described a family of DNA tetrahedra consisting of triangles of DNA helices covalently joined at the vertices to form a mechanically rigid 3D structure. This image of a reduced model of one structure, which is less than 10 nanometers on a side, was created using NanoEngineer-1 Alpha 9. The bowing of the DNA helices is pronounced in this rendering and is the result of electrostatic potential terms included in the customized molecular-mechanics-like force field developed by Dr. K. Eric Drexler specifically for DNA structures. Regarding Turberfield's work, New Scientist wrote:
Now Andrew Turberfield [et al] have shown how carefully crafted DNA structures can be made to self assemble and change shape when sent specific DNA signals. The researchers built tetrahedrons ... using four short DNA "struts" that join at each end. The process exploits the way DNA is held together by complementary bases that form the rungs of a ladder-like structure ... the researchers made cages with two extendible struts that could be independently controlled using different DNA sequences. In theory, it should be possible to create cages in which every strut can be controlled independently, Tuberfield says.These cages are a combination of support material and linear motor, and with the many other DNA tricks being done, they should allow people to build large, complicated, reasonably rigid 3D structures that have controllable moving parts. So this is a very promising development.
A very recent announcement of work by Chad Mirkin and colleagues. They have found a way to use DNA to glue together arbitrary arrangements of teeny gold spheres. People have known for some time now how to make DNA stick to gold spheres, and by careful selection of DNA sequences, Mirkin et al can position groups of spheres in almost any 3D configuration they want.
In light of these developments, Nanorex has narrowed its focus from "general" nanotechnology (anything one might build from common small molecules) to structural DNA nanotechnology. This is likely to be where much progress will occur in the next five years or so. I hope Nanorex will still be around after that, and will be in a good position to shift gears as we move beyond DNA to more general chemistry.
Sunday, February 17, 2008
In twenty years, all the patents for this printer will have expired, and it will be possible for hobbyists to make such pretty stuff at such high resolution. Hmm, thinking more about that inclines me to start an economics blog, since I blog about economics a lot elsewhere.
Friday, February 15, 2008
My hope is that the blue-hatched stage can be made to take either a Dremel tool for CNC milling, or an extruder for fabbing. The result might or might not be self-replicative in a RepRap sense but it would be a cool toy.
Monday, February 11, 2008
It's interesting that you can see the size of the volume pixels Vik is working with. These pieces were printed with polylactic acid, I believe.
Unrelated but cool: Kovio is a non-hobbyist company working on a process to inexpensively print working transistors. Early applications will include smart cards, later you'll see wall-sized displays.
Also unrelated but also cool: Fernando Muñiz has been working with UV-cured resins. This will work a bit like the CandyFab, except the uncured resin is still a liquid so under-support structures are still required. Interesting, I'm not sure if it's better or worse than the FDM approach used by RepRap, Fab@Home, and Tommelise. Also, I don't have any idea how environmentally benign these resins are; it's hard to imagine they're as green as polylactic acid.
Saturday, February 09, 2008
A fabber placing individual drops of building material would be awfully slow for a very large project. One work-around would be to trade away spatial resolution, and let the fabber lay down big handfuls of wet concrete.
Maybe you'd want many fabbers feeding small pieces to an assembler that assembles them into bigger pieces. The assembler must be able to make the small pieces stick together, by gluing them or melting the sides or by using mechanical fasteners such as screws or nuts and bolts. It's possible that the big pieces might then be assembled into very big pieces, and again an assembling machine must be fed from many sources. The assembler would need to be very smart to recognize and correct assembly errors, and would probably need machine vision. This would work well for products from a factory, but might be unsuitable for a house.
A google search for "robot bricklayer" turns up a few modest research efforts. I would have imagined something like the big XYZ stage above with a brick-lifting robot arm, wheeled into position over the site of the future house, but the most advanced effort visible on the web is a standard industrial robot arm picking up bricks instead of doing whatever else robot arms normally do. The arm can't move around the entire volume of the future house, it's not on any sort of XYZ stage, it's just bolted to the floor like any other industrial robot arm. So robotic house construction is still quite a ways off.
Thursday, February 07, 2008
In the Tommelise FAQ, Higgs mentions Linux and Java (which have been adopted by the RepRap project) as presenting a steep learning curve to people without a software background, citing Microsoft Windows and Visual Basic as more user-friendly alternatives. My own early experiences with Linux required enormous patience. Higgs writes Tommelise has been created for people who aren't particularly clever and may be living in modest circumstances. Any open-source "fabber revolution" (1, 2, 3) will be an empty exercise if it fails to serve such people. Then again, if a genuinely open-source revolution is to occur, we'll eventually need to wean ourselves from Microsoft and make our own tools equally user-friendly.
Wednesday, February 06, 2008
They have a great-looking XYZ stage built from a CNC kit. They lower a heating element onto powdered raw material, sintering the raw material as the CandyFab does, except their heating element is a length of nichrome wire instead of a jet of hot air. It gets hot enough to glow, and on the web page they mention that they can work with any powdered material with a melting temperature from 100 to 300 Celsius, including sugar, wax, "Plexi" (plexiglass?), and mixtures such as plastic and sand, plastic and metal powder, powdered paint and sugar powder. Like the CandyFab, each layer of fresh material is laid down on top of the previously worked layer (and I hope that process is automatic as it sounds tedious otherwise) and then you scribble a cross-section on the new layer with the heating element, and then it's time to put down another layer.
The nice thing to this kind of approach is that the unmelted/unfused material provides mechanical support for the built structure. You can build shapes that RepRap and Fab@Home can't make, such as bridges or inverted cones, because any bridge-like part that will go over empty space is built with stuff under it to support it.
This made me curious to start looking around at CNC kits, which could nicely jump-start any fabber project. The XYZ machinery for a fabber is called a "gantry" in CNC language, and there is a very active hobbyist CNC community. Here is a video for a CNC gantry kit that somebody was selling for $195 on eBay. The video itself is for sale ($20) so this is just a teaser.
Here's a few interesting CNC links.